As Seirdy notes:
It just keeps getting more relevant. WhatsApp, GitHub, Twitter, Reddit…each disaster worse than the last. The companies in charge know that the users will just take it after having their autonomy taken first.
You can definitely backup and restore your messages with Signal. I think the app doesn’t allow to export to clear text, but you can use 3rd party tools for extracting the clear text from the backup, such as sigbak.
Plus, the app and protocol are open source, so if a feature has enough demand, someone will eventually implement it.